Process for polymerization with suppressed polymer scale formation

ABSTRACT

A polymer scale preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing: (A) a condensation product of (A-1) a condensate of acetone with a hydroxybenzene compound having at least two hydroxyl groups, and (A-2) an aldehyde compound; (B) an inorganic colloid; and (C) a water-soluble polymeric compound. This agent is used for forming a coating on the inner wall, etc. of a polymerization vessel. Such a vessel is effective in preventing polymer scale deposition, not only on the areas in the liquid-phase region but also on the areas around the interface between the gas and liquid phases in the vessel, and useful in producing a polymer that shows very few fish eyes and good whiteness when formed into sheets or the like.

This application is a continuation Ser. No. 08/149,774, filed on Nov.10, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polymer scale preventive agent foruse in polymerization of a monomer having an ethylenically unsaturateddouble bond, a polymerization vessel effective in preventing polymerscale deposition, and a process for producing a polymer using the same.

2. Description of the Prior Art

Heretofore, methods for polymerization of a monomer having anethylenically unsaturated double bond have been known, such assuspension, emulsion, solution, gas phase and bulk polymerizationprocesses and the like. In any of these polymerization processes,polymer scale is liable to be deposited on the areas with which themonomer comes into contact, such as inner walls, stirring equipment andso on of a polymerization vessel.

The deposition of the polymer scale results in disadvantages that theyield of the polymer and cooling capacity of the polymerization vesselare lowered, and that the polymer scale may peel off and mix into apolymeric product, thereby impairing the quality of formed productsobtained by processing the polymeric product. In addition, removal ofdeposited polymer scale is very laborious and time-consuming. Further,the polymer scale contains unreacted monomers and, therefore, may causephysical disorders in the operators, which has been a very seriousproblem in recent years.

For preventing polymer scale deposition on the polymerization vesselinner wall and so forth, methods have been known, for example, a methodin which a polymer scale preventive agent comprising a polar organiccompound such as amine compounds, quinone compounds, aldehyde compounds,etc. is applied to the polymerization vessel inner wall and so on toform a coating and a method in which such compounds are added to anaqueous medium for suspension polymerization (Japanese PatentPublication (KOKOKU) No. 45-30343 (1970)), as practiced in someinstances of suspension polymerization of vinyl chloride.

However, these methods have the disadvantage that, although the polymerscale preventive effect is exhibited while polymerization is repeatedfor up to about 5 or 6 batches, the effect diminishes if the number ofrepeated batches of polymerization exceeds 5 or 6 (that is, the scalepreventive effect is poor in durability). The disadvantage is emphasizedparticularly where a water-soluble catalyst is used for polymerization,and, in this point, the polymer scale prevention according to thesemethods is unsatisfactory industrially.

For overcoming the above disadvantage, methods have been proposed inwhich the inner wall of a polymerization vessel is coated with a polymerscale preventive agent whose effective constituent is, for example, acondensation product of an aromatic amine compound and an aromatic nitrocompound (Japanese Patent Publication (KOKOKU) No. 60-30681 (1985)), areaction product of a phenolic compound with an aromatic aldehyde(Japanese Pre-examination Patent Publication (KOKAI) No. 57-192414(1982)), a reaction product of a polyhydric phenol with an aliphaticaldehyde (Japanese Patent Publication (KOHYO) No. 57-502169 (1982)), areaction product of 1-naphthol with formaldehyde (Japanese PatentPublication (KOKOKU) No. 01-31523 (1989)), or the like. Where one ofthese known polymer scale preventive agents is applied to the areas withwhich monomers come into contact, such as the inner wall surface of apolymerization vessel, and a coating is thereby formed, it is possibleto repeat about 100 to 200 batches of polymerization without causingdeposition of polymer scale on the areas located in the liquid-phaseregion inside the polymerization vessel. Besides, even in theabove-mentioned case where a water-soluble catalyst is used, depositionof polymer scale in the liquid-phase region is similarly prevented.

However, even if the coating is formed by use of the polymer scalepreventive agent containing such an effective component as thecondensation product of an aromatic amine compound and an aromatic nitrocompound, etc. as mentioned above, there remains a drawback that polymerscale deposition may occur on the areas around the interface between theliquid phase and the gas phase located at an upper portion of theinterior of the polymerization vessel.

Once polymer scale deposition occurs around the interface between thegas and liquid phases, the deposited scale will grow gradually aspolymerization runs are repeated, and at last it may peel off to beincorporated into the polymeric product. If the polymeric product withthe polymer scale thus mixed therein is processed into formed productssuch as sheets or the like, the polymer scale causes generation of manyfish eyes in the formed products, thereby lowering seriously the qualityof the formed products.

Besides, where a polymeric product is processed into formed productssuch as sheets, etc., the formed products are required to have a highwhiteness. That is, when a polymeric product formed into a sheet or thelike without any addition of a coloring agent, the resulting formedproduct is more or less colored and such coloration, called initialcoloration, is desired to be as slight as possible. However, the coatingformed by using the polymer scale preventive agent containing such aneffective component as the condensation product of an aromatic aminecompound and an aromatic nitro compound, etc. as above mentioned may mixinto a polymeric product through peeling or dissolution, therebylowering the whiteness, or increasing the initial coloration, of theresulting formed products.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a polymer scalepreventive agent for use in polymerization of a monomer having anethylenically unsaturated double bond that can prevent effectively thedeposition of polymer scale, not only on the areas in the liquid-phaseregion but also on the areas around the interface between the gas andliquid phases inside a polymerization vessel, and that makes it possibleto produce a polymer having a very small number of fish eyes and slightinitial coloration when processed into formed products such as sheets orthe like; and a polymerization vessel and a process for producing apolymer which utilize the polymer scale preventive agent.

In order to attain the above object, the present invention provides apolymer scale preventive agent for use in polymerization of a monomerhaving an ethylenically unsaturated double bond, comprising an alkalinesolution containing:

(A) a condensation product of

(A-1) a condensate of acetone with a hydroxybenzene compound having atleast two hydroxyl groups, and

(A-2) an aldehyde compound,

(B) an inorganic colloid, and

(C) a water-soluble polymeric compound.

Also, the present invention provides a polymerization vessel forpolymerizing a monomer having an ethylenically unsaturated double bond,comprising a coating on its inner wall surfaces,

wherein said coating has been formed by applying an alkaline solutioncontaining:

(A) a condensation product of

(A-1) a condensate of acetone with a hydroxybenzene compound having atleast two hydroxyl groups, and

(A-2) an aldehyde compound,

(B) an inorganic colloid, and

(C) a water-soluble polymeric compound, followed by drying.

Further, the present invention provides a process for producing apolymer of a monomer having an ethylenically unsaturated double bond,which comprises polymerizing the monomer in a polymerization vesselhaving a coating on its inner wall surfaces, whereby polymer scale isprevented from being deposited,

wherein said coating has been formed by applying an alkaline solutioncontaining:

(A) a condensation product of

(A-1) a condensate of acetone with a hydroxybenzene compound having atleast two hydroxyl groups, and

(A-2) an aldehyde compound,

(B) an inorganic colloid, and (C) a water-soluble polymeric compound,followed by drying.

According to the present invention, deposition of polymer scale in apolymerization vessel can be effectively prevented, not only on theareas in the liquid-phase region but also on the areas around theinterface between the gas phase and the liquid phase. Therefore, wherepolymerization is conducted by applying the present invention, theoperation of removing polymer scale need not be performed every run ofpolymerization and, as a result, productivity is improved.

In addition, the polymeric product obtained by application of thepresent invention can be formed into sheets or the like which have veryfew fish eyes. Besides, the formed products are good in regard ofinitial coloration property. More specifically, such formed productshave a luminosity index (L value) in the Hunter's color differenceequation described in JIS Z 8730 (1980) of, for example, at least 70 inthe case of vinyl chloride polymer, and at least 80 in the case of SBR.

Furthermore, according to the present invention, the coating liquid usedfor forming the coating comprises water as a major component and,therefore, can be used under conditions such that there is little fearof organic-solvent inflammation, explosion or the like and there is noproblem as to safety in handling, such as toxicity.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(A) Condensation product

(A-1) Condensate of acetone with a hydroxybenzene compound havinq atleast two hydroxyl groups

Hydroxybenzene compound havinq at least two hydroxyl groups:

The hydroxybenzene compound having at least two hydroxyl groups is, forexample, a compound having the following general formula (1): ##STR1##wherein R¹ group or groups, which may be the same or different from eachother, are each a group selected from the group consisting of --H andalkyl groups of 1 to 5 carbon atoms, and k is an integer from 2 to 6.

Specific examples of the hydroxybenzene compound of the general formula(1) include pyrogallol, hydroxyhydroquinone, resorcinol,4-methylresorcinol, and the like. Among these, preferred is pyrogallol.

Condensate:

The condensate (A-1) of acetone with a hydroxybenzene compound having atleast two hydroxyl groups may be, for example, a condensate of acetonewith pyrogallol, which normally contains from 0.1 to 10 moles of theacetone component per mole of the pyrogallol component and ordinarilyhas a melting point of from 100° to 500° C. The greater the molecularweight of the condensate (A-1), the higher the melting point. Forexample, in the case of pyrogallol-acetone condensates, a melting pointof from 160° to 170° C corresponds to a molecular weight of from 1450 to1650, and a melting point of from 200° to 220° C. corresponds to amolecular weight of from 2600 to 4000.

The condensate (A-1) as above can be produced by dissolving thehydroxybenzene compound in acetone and permitting condensation toproceed in the presence of a catalyst, normally at a temperature rangingfrom room temperature to 100° C. for a time period of 0.5 to 300 hours.The amount of the hydroxybenzene compound to be used for thecondensation is normally from 1 to 100 parts by weight per 100 parts byweight of acetone. As the catalyst, for example, phosphorus oxychlorideand the like may be used.

As the above-mentioned condensate in which the hydroxybenzene compoundis pyrogallol, commercial products (for example, pyrogallol-acetoneresins produced by Fuji Chemicals Ind. Co., Ltd.) are available and canbe used.

The condensates (A-1) as above may be used either singly or incombination of two or more.

(A-2) Aldehyde compound

The aldehyde compound (A-2) is an organic compound having at least onealdehyde group (--CHO group), preferably one or two aldehyde groups.

The aldehyde compound includes, for example, the compounds of thefollowing general formulas (2) to (4):

    R.sup.2 --CHO (2 )

wherein R² is a group selected from the group consisting of --H, --COOH,--CHO, substituted alkyl groups of from 1 to 5 carbon atoms, andunsubstituted alkyl groups of from 1 to 5 carbon atoms; ##STR2## whereinR³ group or groups, which may be the same or different from each other,are each a group selected from the group consisting of --H and --OH, andm is an integer from 1 to 6; and ##STR3## wherein R⁴ group or groups,which may be the same or different from each other, are each a groupselected from the group consisting of --H and alkyl groups of 1 to 5carbon atoms, and n is an integer from 1 to 4.

Specific examples of the compounds of the above general formula (2)include formaldehyde, acetaldehyde, glyoxylic acid, glyoxal, and thelike; specific examples of the compounds of the above general formula(3) include benzaldehyde, salicylaldehyde, phthalaldehyde and the like;and specific examples of the compounds of the above general formula (4)include heterocyclic aldehydes such as furfural and5-methyl-2-furaldehyde, and so forth. Among these, preferred areformaldehyde, glyoxylic acid, benzaldehyde, salicylaldehyde, andfurfural.

The aldehyde compounds (A-2) as above may be used either singly or incombination of two or more.

Preparation of condensation product (A) of condensate (A-1) and aldehydecompound (A-2)

The condensation product (A) can be obtained by condensing thecondensate (A-1) with the aldehyde compound (A-2). The condensation ofthe condensate (A-1) and aldehyde compound (A-2) may be carried out byreacting them in water in the presence of a catalyst, normally at atemperature of 50° to 150° C. for a time period of 1 to 20 hours,preferably at 60° to 120° C. for 2 to 10 hours.

The catalyst for the condensation includes, for example, acid catalystssuch as phosphoric acid, sulfuric acid, hydrochloric acid, etc., andbase catalysts such as NaOH, KOH, LiOH, NH3, etc. The condensate (A-1)is insoluble in acidic aqueous mediums but is soluble in alkalineaqueous mediums; therefore, the condensation reaction is difficult tocarry out in the presence of an acid catalyst but easy to carry out inthe presence of a base catalyst. From this point of view, it ispreferable to conduct the condensation reaction in the presence of abase catalyst.

In preparing the condensation product (A), the condensate (A-1) andaldehyde compound (A-2) are used in amounts which depend on the kinds ofthe condensate (A-1), aldehyde compound (A-2) and catalyst used,reaction temperature, reaction time and so forth. The aldehyde compound(A-2) is preferably used in an amount of from 0.1 to 10 moles, morepreferably from 0.3 to 3 moles, per mole of the condensate (A-1). If theamount of the aldehyde compound (A-2) is too large or too small, theresulting condensation product (A) will give a lowered polymer scalepreventive effect when formulated into a polymer scale preventive agent.

The amount of the catalyst to be used for the condensation reaction isnot particularly limited, and is preferably from 0.1 to 10 moles, morepreferably from 0.5 to 5 moles, per mole of the condensate (A-1).

(B) Inorqanic colloid

The inorganic colloid (B) is a particulate colloid produced by adispersing method with water as dispersion medium or by a condensingmethod, the size of colloidal particles being from 1 to 500 mμ.

Specific examples of the inorganic colloid include colloids of metaloxides and hydroxides, the metal being selected from the groupconsisting of aluminum, thorium, titanium, zirconium, antimony, tin,iron and the like; colloids of tungstic acid, vanadium pentoxide, goldand silver; silver iodide sols; colloids of selenium, sulfur, silica andthe like; and so on. Among these, preferred are colloids of a metaloxide or hydroxide, the metal being selected from the group consistingof aluminum, titanium, zirconium, tin and iron, and colloidal silica.

The inorganic colloids (B) as above may be used either singly or incombination of two or more.

(C) Water-soluble polymeric compound

The water-soluble polymeric compound (C) includes, for example,amphoteric polymeric compounds such as gelatin, casein, etc.; anionicpolymeric compounds such as polyacrylic acid, polystyrenesulfonic acid,carboxymethyl cellulose, alginic acid, etc.; cationicnitrogen-containing polymeric compounds such as polyvinyl pyrrolidone,chitosan, polyacrylamide, etc.;hydroxyl group-containing polymericcompounds such as polyvinyl alcohol, hydroxyethyl cellulose,hydroxypropyl cellulose, pectin, etc.; and so forth.

Among the water-soluble polymeric compounds (C) as above, preferred aregelatin, casein, polyacrylic acid, carboxymethyl cellulose, polyvinylpyrrolidone and pectin.

The water-soluble polymeric compounds (C) may be used either singly orin combination of two or more.

Preparation of polymer scale preventive aqent

The polymer scale preventive agent according to the present inventioncomprises an alkaline solution containing the above-describedcondensation product (A), inorganic colloid (B), and water-solublepolymeric compound (C). The polymer scale preventive agent is applied toinner wall surfaces of a polymerization vessel and the like, followed bydrying to form a coating, whereby polymer scale can be prevented frombeing deposited on the polymerization vessel inner wall or the like.

The polymer scale preventive agent is prepared, for example, by addingan aqueous medium to the above-described condensation product (A),inorganic colloid (B) and water-soluble polymeric compound (C) followedby mixing, and controlling the pH of the resulting liquid mixture intoan alkaline range.

Where the condensation product (A) for use in preparing the polymerscale preventive agent is produced by using a base catalyst, thecondensation reaction mixture containing the condensation product (A)upon completion of the condensation reaction is alkaline and, hence, canbe used directly for preparation of the polymer scale preventive agent.On the other hand, where the condensation product (A) is produced byusing an acid catalyst, the condensation reaction mixture obtained istreated to remove the solvent therefrom, then the condensation product(A) is washed and is vacuum dried at low temperature, before being usedfor preparation of the polymer scale preventive agent.

As the aqueous medium for preparation of the polymer scale preventiveagent, water may normally be used. Also usable as the aqueous medium aremixed solvents of water and an organic solvent miscible with water. Theorganic solvents miscible with water include, for example, alcohols suchas methanol, ethanol, propanol and the like, ketones such as acetone,methyl ethyl ketone and the like, and esters such as methyl acetate andthe like. Where such mixed solvent of water and an organic solventmiscible with water is used, the amount of the organic solvent in themixed solvent is selected so that there will be little danger ofinflammation, explosion or the like and no problems as to safety inhandling, such as toxicity. Specifically, the amount of the organicsolvent contained in the mixed solvent is preferably 50% by weight orless, and more preferably 30% by weight or less.

The polymer scale preventive agent has a pH in an alkaline range,preferably from 9 to 14, more preferably from 11 to 13. The adjustmentof pH into the alkaline range can be made by use of an alkaline compoundsuch as NaOH, KOH, LiOH, NH₃ and the like.

The amount of the component (B) in the polymer scale preventive agent isnormally from 0.1 to 1000 parts by weight, and preferably from 1 to 600parts by weight, per 100 parts by weight of the component (A). Theamount of the component (C) is normally from 0.1 to 1000 parts byweight, and preferably from 1 to 300 parts by weight, per 100 parts byweight of the component (A). If the amount of the component (B) and/orthe component (C) relative to the amount of the component (A) is toolarge or too small, it may be impossible to obtain the polymer scalepreventive effect.

The total concentration of the components (A), (B) and (C) in thepolymer scale preventive agent is not particularly limited, as long asthe total coating weight described later can be obtained. The totalconcentration is normally from about 0.005% to about 10% by weight, andpreferably from about 0.03% to about 2.0% by weight.

Formation of coatinq

To form a coating on inner wall surfaces of a polymerization vesselusing the polymer scale preventive agent prepared as above-described,first the agent is applied to the inner wall surfaces of thepolymerization vessel. Then, the applied agent is dried sufficiently ata temperature ranging, for example, from room temperature to 100° C.,optionally followed by washing with water.

The polymer scale preventive agent is preferably applied to not only theinner wall surfaces of a polymerization vessel but also other areas withwhich the monomer comes into contact during polymerization, for example,stirring blades, stirring shaft, baffles, condensers, headers, searchcoil, bolts, nuts, etc.

More preferably, for formation of the coating, the polymer scalepreventive agent is applied to areas with which the monomer does notcome into contact during polymerization but on which polymer scale maybe deposited, for example, the inner surfaces, etc. of equipment andpipes of an unreacted monomer recovery system. Specifically, such areasinclude the inner surfaces of monomer distillation columns, condensers,monomer stock tanks, valves, and so on.

The method of applying the polymer scale preventive agent to the innerwall surfaces of a polymerization vessel is not particularly restricted,and includes, for example, brush coating, spray coating, a method byfilling the polymerization vessel with the polymer scale preventiveagent followed by withdrawal thereof, and the automatic coating methodsas disclosed in Japanese Pre-examination Patent Publication (KOKAI) Nos.57-61001 (1982) and 55-36288 (1980), Japanese Patent Publication (KOHYO)Nos. 56-501116 (1981) and 56-501117 (1981), and Japanese Pre-examinationPatent Publication (KOKAI) No. 59-11303 (1984), etc.

The method of drying wet coated surfaces provided by application of thepolymer scale preventive agent, is not restricted, either. For example,the following methods can be used: a method in which, after the agent isapplied, hot air with a suitable elevated temperature is blown to thecoated surface; a method in which the inner wall surfaces of apolymerization vessel and the surfaces of other parts to be coated arepreliminarily heated, for example, to a temperature of 30° to 80° C.,and the polymer scale preventive agent is directly applied to the heatedsurfaces; and so on. After dried, the coated surfaces are washed withwater if necessary.

The coating obtained in this manner has a total coating weight afterdried of normally from 0.001 to 5 g/m² and preferably from 0 05 to 2g/m².

The formed coating has good durability and retains the polymerscale-preventing action; therefore, the above-described coatingoperation may not necessarily be carried out every batch ofpolymerization. Accordingly, productivity is improved.

Polymerization

After the formation of the coating on the inner wall surfaces of apolymerization vessel, and preferably also on other areas with whichmonomer may come into contact during polymerization, etc. by the coatingoperation as above, polymerization is carried out in accordance withconventional procedures. That is, a monomer having an ethylenicallyunsaturated double bond, a polymerization initiator (catalyst), andoptionally a polymerization medium such as water, etc., a dispersingagent such as suspending agents, solid dispersing agents, nonionic oranionic emulsifying agents, etc., and the like are charged into thepolymerization vessel, and then polymerization is carried out accordingto conventional procedures.

The monomers having an ethylenically unsaturated double bond which canbe polymerized by applying the process of the present invention include,for example, vinyl halides such as vinyl chloride and the like; vinylesters such as vinyl acetate, vinyl propionate and the like; acrylicacid, methacrylic acid, and their esters and salts; maleic acid, fumaricacid, and their esters and anhydrides; diene monomers such as butadiene,chloroprene, isoprene and the like; styrene; acrylonitrile; vinylidenehalides; vinyl ethers; and so forth.

These monomers may be used either singly or in combination of two ormore.

There are no particular restrictions on the type of polymerization towhich the process according to the present invention can be applied.That is, the process of the present invention is effective in any ofsuch polymerization types as suspension polymerization, emulsionpolymerization, solution polymerization, bulk polymerization, and gasphase polymerization. Particularly, the process of the present inventionis more suitable to polymerizations in an aqueous medium, such assuspension polymerization and emulsion polymerization.

In the following, general procedures of polymerization are describedwith reference to each type of polymerization.

In suspension and emulsion polymerizations, first, water and adispersing agent are charged into a polymerization vessel, andthereafter a polymerization initiator is charged. Subsequently, thepolymerization vessel is evacuated to reduce the internal pressure to avalue of 0.1 to 760 mmHg, and a monomer is then charged (whereupon theinternal pressure usually takes a value of from 0.5 to 30 kgf/cm².G).Thereafter, polymerization is carried out at a reaction temperature offrom 30° to 150° C. During the polymerization, one or more of water, adispersing agent and a polymerization initiator may be added, ifnecessary. Reaction temperature during the polymerization is differentdepending on the kind of monomer to be polymerized. For example, in thecase of polymerizing vinyl chloride, polymerization is carried out at30° to 80° C.; in the case of polymerizing styrene, polymerization iscarried out at 50° to 150° C. The polymerization may be judged to becompleted when the pressure inside the polymerization vessel has fallento a value of 0 to 7 kgf/cm2.G or when cooling water which is let flowinto and out of a jacket provided around the polymerization vessel hascome to show approximately equal inlet and outlet temperatures (i.e.,when liberation of heat due to polymerization reaction has subsided).The amounts of the water, dispersing agent and polymerization initiatorto be charged for polymerization are 20 to 500 parts by weight, 0.01 to30 parts by weight, and 0.01 to 5 parts by weight, respectively, per 100parts by weight of the monomer.

In solution polymerization, an organic solvent such as toluene, xylene,pyridine, etc. is used as the polymerization medium, in place of water.A dispersing agent may be used, if necessary. The other conditions forpolymerization are generally the same as those described for suspensionand emulsion polymerizations.

In bulk polymerization, after a polymerization vessel is evacuated to apressure of from about 0.01 mmHg to about 760 mmHg, a monomer and apolymerization initiator are charged into the polymerization vessel, andthen polymerization is carried out at a reaction temperature of from-10° C. to 250° C. For example, the reaction temperature is 30° to 80°C. for polymerization of vinyl chloride, and is 50° to 150° C. forpolymerization of styrene.

Where polymerization is carried out by applying the process of thepresent invention, it is possible to prevent polymer scale from beingdeposited, regardless of the materials of the inner wall, etc. of apolymerization vessel. For example, where the polymerization vessel ismade of a stainless steel or other steel as well as where thepolymerization vessel is a glass-lined one or the like, the polymerscale deposition can be prevented from occurring during polymerization.

Those additive materials which are conventionally added inpolymerization systems can be used without any limitations. That is tosay, the process of the present invention can effectively preventpolymer scale deposition in polymerization systems which may containadditive materials including, for example, polymerization initiatorssuch as t-butyl peroxyneodecanoate, bis(2-ethylhexyl) peroxydicarbonate,3,5,5-trimethylhexanoyl peroxide, α-cumyl peroxyneodecanoate, cumenehydroperoxide, cyclohexanone peroxide, t-butyl peroxypivalate,bis(2-ethoxyethyl) peroxydicarbonate, benzoyl peroxide, lauroylperoxide, 2,4-dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate,α,α'-azobis-isobutyronitrile, α,α'-azobis-2,4-dimethylvaleronitrile,potassium peroxodisulfate, ammonium peroxodisulfate, p-menthanehydroperoxide, etc.; suspending agents comprised of, for example,natural or synthetic polymeric compounds such as partially saponifiedpolyvinyl alcohols, polyacrylic acids, vinyl acetate/maleic anhydridecopolymers, cellulose derivatives (e.g. hydroxypropyl methyl cellulose),pyrogallol-acetone resins, etc.; solid dispersing agents such as calciumphosphate, hydroxyapatite, etc.; nonionic emulsifying agents such assorbitan monolaurate, sorbitan trioleate, polyoxyethylene alkyl ether,etc.; anionic emulsifying agents such as sodium lauryl sulfate, sodiumalkylbenzenesulfonates (e.g. sodium dodecylbenzenesulfonate), sodiumdioctylsulfosuccinate, etc.; fillers such as calcium carbonate, titaniumoxide, etc.; stabilizers such as tribasic lead sulfate, calciumstearate, dibutyltin dilaurate, dioctyltin mercaptide, etc.; lubricantssuch as rice wax, stearic acid, cetyl alcohol, etc.; plasticizers suchas DOP, DBP, etc.; chain transfer agents such as mercaptans (e.g.t-dodecyl mercaptan), trichloroethylene, etc.; pH adjusters, and soforth.

Besides, the polymer scale preventive agent of the present invention maybe added to the medium for polymerization. In that case, for example,the polymer scale preventive agent is used in the coating operation and,moreover, a small amount of the agent is added to the medium forpolymerization. Where such addition of the agent to the polymerizationmedium as well as the coating operation is carried out, the resultingscale preventive effect is higher than that attainable by the coatingoperation alone. In the case of adding the polymer scale preventiveagent in the form of a solution to the medium for polymerization, theaddition amount may be in the range from 5 to 1000 ppm based on thetotal weight of the monomer or monomers having an ethylenicallyunsaturated double bond which are charged into the polymerizationvessel.

EXAMPLES

The present invention will now be described in detail below, referringto examples thereof and comparative examples. In each table below,experiments marked with * on their number (No.) are comparative examplesand the other experiments are working examples of the present invention.

Preparation of Condensation Product No. 1

A 2-liter, three-necked separable flask equipped with a refluxcondenser, thermometer and stirrer was charged with water (1 liter), apyrogallol-acetone resin (product code: PA-1, a product by FujiChemicals Ind. Co., Ltd.; m.p. 160°-170° C.) (1 mole) as condensate(A-1), formaldehyde (1.2 moles) as aldehyde compound (A-2), and NaOH(0.8 mole) as base catalyst. Subsequently, while the flask was heated onan oil bath at 85° C., the reaction mixture in the flask was reactedwith stirring under a stream of nitrogen for 6 hours, followed bycooling. A solution of Condensation Product No. 1 was thus obtained.

Preparation of Condensation Product Nos. 2 to 7

Solutions of Condensation Product Nos. 2 to 7 were produced in the samemanner as the solution of Condensation Product No. 1, except for usingthe condensate (A-1), aldehyde compound (A-2), catalyst and solvent asshown in Table 1. In Table 1, PA-2 (product code) is a pyrogallolacetoneresin with a melting point of 200°-220° C. (produced by Fuji ChemicalsInd. Co., Ltd.).

Also shown in Table 1 are the total concentration of(A-1)+(A-2)+catalyst, molar ratio of (A-1):(A-2):catalyst, reactiontemperature, and reaction time.

                                      TABLE 1                                     __________________________________________________________________________    (A)                                                                           Condensation                                                                         (A-1)                                                                              (A-2)             Total conc. of         Reaction                                                                           Reaction            product                                                                              Conden-                                                                            Aldehyde                                                                            Catalyst    (A-1) + (A-2) + Catalyst                                                                   (A-1):(A-2):Catalyst                                                                    temp.                                                                              time                No.    sate compound                                                                            Acid                                                                             Base                                                                              Solvent                                                                            (mol/l)      (mol. ratio)                                                                            (°C.)                                                                       (hr)                __________________________________________________________________________    1      PA-1 Formalde-                                                                           -- NaOH                                                                              Water                                                                              3.0          1:1.2:0.8 85   6                               hyde                                                              2      PA-1 Benzalde-                                                                           -- NaOH                                                                              Water                                                                              3.0          1:1:1.2   90   6                               hyde                                                              3      PA-1 Glyoxylic                                                                           -- NaOH                                                                              Water                                                                              3.0          1:1:1     90   6                               acid                                                              4      PA-1 Salicyl-                                                                            -- NaOH                                                                              Water                                                                              3.0          1:1:1     90   6                               aldehyde                                                          5      PA-2 Formalde-                                                                           -- NaOH                                                                              Water                                                                              3.0          1:1:1.1   95   7                               hyde                                                              6      PA-2 Glyoxylic                                                                           -- KOH Water                                                                              3.0          1:1:1.2   95   7                               acid                                                              7      PA-2 Salicyl-                                                                            -- KOH Water                                                                              3.0          1:1:1     95   7                               aldehyde                                                          __________________________________________________________________________

Example 1 (Experiment Nos. 101-110)

A stainless steel polymerization vessel having an internal capacity of2000 liters and equipped with a stirrer was used in each of theseexperiments.

In each experiment, a polymer scale preventive agent was prepared byusing the condensation product (A), inorganic colloid (B), water-solublepolymeric compound (C), solvent and alkaline compound as given in Table2 in such amounts as to satisfy the conditions (total concentration of(A)+(B)+(C), weight ratio of (A):(B):(C), solvent composition, and pH)as given in Table 2. The inorganic colloids (a to g, in Table 2 andTable 5) which were used in this Example 1 and in Example 2 (which willbe described below) are as set forth in Table 4. The polymer scalepreventive agents thus prepared were each applied to the inner wall ofthe polymerization vessel and to the areas with which monomer comes intocontact during polymerization, such as the stirring blades, stirringshaft, etc., and dried by heating at 50° C. for 15 minutes to form acoating, followed by washing the inside of the polymerization vesselwith water.

Thereafter, in each experiment, polymerization was carried out asfollows. The polymerization vessel having the coating formed by theabove coating treatment was charged with 800 kg of water, 400 kg ofvinyl chloride, 500 g of a partially saponified polyvinyl alcohol, 50 gof hydroxypropyl methyl cellulose and 140 g of 3,5,5-trimethylhexanoylperoxide, and polymerization was carried out with stirring at 66° C. for6 hours. After the polymerization was over, the produced polymer andunreacted monomer were recovered, the inside of the polymerizationvessel was washed with water, and residual resin was removed.

A batch of operations from the formation of the coating throughpolymerization to washing the inside of the polymerization vessel withwater as described above was repeated, the number of repeated batchesbeing given in Table 3.

In each experiment, after the final batch was over, the amount ofpolymer scale deposited on the areas located in the liquid-phase regionin the polymerization vessel and the amount of polymer scale depositedon the areas around the interface between the gas and liquid phases inthe polymerization vessel were determined according to the method asfollows. The results are given in Table 3.

Measurement of the amount of polymer scale deposited

The scale deposited in an area of 10 cm square at a predeterminedlocation on the inner wall of a polymerization vessel is scraped offwith a stainless steel spatula as completely as can be confirmed withthe naked eye, and then the scraped scale is weighed on a balance. Themeasured value is multiplied by 100 to obtain the amount of thedeposited polymer scale per area of 1 m².

Besides, the number of fish eyes which may appear when a polymer isformed into sheet was measured with respect to the polymers produced inthe experiments, according to the method below. The results are given inTable 3.

Measurement of fish eyes

A hundred (100) parts by weight of a polymer, 50 parts by weight ofdioctyl phthalate (DOP), 1 part by weight of dibutyltin dilaurate, 1part by weight of cetyl alcohol, 0.25 part by weight of titanium oxideand 0.05 part by weight of carbon black are formulated to prepare amixture. The mixture is kneaded at 150° C. for 7 minutes with 6 inchrolls, and then formed into a sheet 0.2 mm thick. The obtained sheet isexamined for the number of fish eyes per 100 cm² by light transmission.

Further, to evaluate initial coloration property at the time a polymeris formed into sheet, luminosity index (L value) was measured withrespect to the polymers produced in the experiments, according to themethod below. The results are given in Table 3.

Measurement of luminosity index (L value)

A hundred (100) parts by weight of a polymer, 1 part by weight of a tinlaurate stabilizing agent (product code: TS-101, a product by AkisimaChemical Co.) and 0.5 part by weight of a cadmium stabilizing agent(product code: C-100J, a product by Katsuta Kako Co.), and 50 parts byweight of dioctyl phthalate as a plasticizer are kneaded at 160° C. for5 minutes with a twin roll mill, and then formed into a sheet 1 mmthick. Subsequently, this sheet is placed in a mold measuring 4×4×1.5cm, heated at 160° C. under a pressure of 65 to 70 kgf/cm² for 0.2 hourand press molded under the same conditions to prepare a test specimen.This test specimen is measured for luminosity index L in the Hunter'scolor difference equation described in JIS Z 8730 (1980). The greaterthe value of L, the higher the whiteness evaluated, namely, the betterthe initial coloration property evaluated.

The value of L is determined as follows.

The stimulus value Y of XYZ color system is determined by thephotoelectric tristimulus colorimetry using the standard light C,photoelectric colorimeter (Color measuring color difference meter ModelZ-1001DP, produced by Nippon Denshoku Kogyo K.K.) in accordance with JISZ 8722. As the geometric condition for illumination and beingilluminated, the condition d defined in section 4.3.1 of JIS Z 8722 isadopted. From the stimulus value Y obtained, the L value is calculatedbased on the equation: L=10Y^(1/2) described in JIS Z 8730 (1980).

                                      TABLE 2                                     __________________________________________________________________________    Polymer scale preventive agent                                                   (A)         (C)        Total conc.                                            Condensation                                                                         (B)  Water-soluble                                                                            of                                                  Exp.                                                                             product                                                                              Inorganic                                                                          polymeric  (A) + (B) + (C)                                                                        (A):(B):(C)                                                                         Solvent     Alkaline                 No.                                                                              No.    colloid                                                                            compound   (wt. %)  (wt. ratio)                                                                         (weight ratio)                                                                            compound                                                                            pH                 __________________________________________________________________________    101*                                                                             1      --   --         0.3      100:--:100                                                                          Water:Methanol                                                                            NaOH10)                                                                             12.5               102*                                                                             1      b    --         0.3      100:100:--                                                                          Water:Methanol                                                                            NaOH10)                                                                             12.5               103*                                                                             1      --   Polyacrylic acid                                                                         0.3      100:--:100                                                                          Water:Methanol                                                                            NaOH10)                                                                             12.5               104                                                                              1      b    Polyacrylic acid                                                                         0.3      100:100:100                                                                         Water:Methanol                                                                            NaOH10)                                                                             12.5               105                                                                              2      a    Polyvinyl pyrrolidone                                                                    0.3      100:50:50                                                                           Water:Methanol                                                                            NaOH30)                                                                             12.5               106                                                                              3      c    Polyvinyl alcohol                                                                        0.3      100:50:100                                                                          Water:Methanol                                                                            NaOH20)                                                                             12.5               107                                                                              4      d    Gelatin    0.3      100:150:50                                                                          Water:Acetone (80:20)                                                                     NaOH  12.5               108                                                                              5      e    Casein     0.3      100:150:100                                                                         Water:Methanol                                                                            NaOH10)                                                                             12.5               109                                                                              6      f    Pectin     0.2      100:100:50                                                                          Water:Methanol                                                                            NaOH10)                                                                             12.5               110                                                                              7      g    Na salt of carboxy-                                                                      0.2      100:50:50                                                                           Water:Methanol                                                                            NaOH20)                                                                             12.5                              methyl cellulose                                               __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________              Results of polymerization                                           Number of Polymer scale amount (g/m.sup.2)                                                              Number of                                                                            Luminosity                                   Exp.                                                                             repeated                                                                             Liquid                                                                            Around interface of                                                                       fish   index                                        No.                                                                              batches                                                                              phase                                                                             gas and liquid phases                                                                     eyes   (L value)                                    __________________________________________________________________________    101*                                                                              40    6   400         45     72.5                                         102*                                                                              60    3   120         37     72.5                                         103*                                                                              50    3   170         40     72.5                                         104                                                                              200    0   4           8      72.5                                         105                                                                              200    0   4           8      72.0                                         106                                                                              160    0   6           8      72.0                                         107                                                                              200    0   6           6      72.0                                         108                                                                              200    0   6           7      72.0                                         109                                                                              160    0   6           7      72.0                                         110                                                                              160    0   5           8      72.0                                         __________________________________________________________________________

                  TABLE 4                                                         ______________________________________                                        Diameter of   Name                                                            colloidal     of                                                              particles (mμ)                                                                           article      Manufacturer                                       ______________________________________                                        a    10-20        Snowtex O    Nissan Chemical                                                  (colloidal silica)                                                                         Industries, Ltd.                               b    5-7          Snowtex CXS-9                                                                              Nissan Chemical                                                  (colloidal silica)                                                                         Industries, Ltd.                               c    100-200      Titanium oxide                                                                             Nissan Chemical                                                               Industries, Ltd.                               d    10-20        Aluminum oxide                                                                             Nissan Chemical                                                               Industries, Ltd.                               e    60-70        Zirconium oxide                                                                            Nissan Chemical                                                               Industries, Ltd.                               f    20-50        Tin oxide    Nissan Chemical                                                               Industries, Ltd.                               g    10-15        Iron hydroxide                                                                             produced by the                                                               present inventors                              ______________________________________                                    

Example 2 (Experiment Nos. 201-207)

A stainless steel polymerization vessel having an inner capacity of 20liters and equipped with a stirrer was used in each of theseexperiments.

In each experiment, a polymer scale preventive agent was prepared byusing the condensation product (A), inorganic colloid (B), water-solublepolymeric compound (C), solvent, and alkaline compound as given in Table5 in such amounts as to satisfy the conditions (total concentration of(A)+(B)+(C), weight ratio of (A):(B):(C), solvent composition, and pH)as given in Table 5. The polymer scale preventive agents were eachapplied to the inner wall, the stirring shaft, the stirring blades andother areas with which a monomer comes into contact of thepolymerization vessel, and dried by heating at 50° C. for 15 minutes toform a coating, followed by washing the inside of the polymerizationvessel with water.

Subsequently, in each experiment, the polymerization vessel providedwith the coating by the coating treatment as above was charged with 9 kgof water, 225 g of sodium dodecylbenzenesulfonate, 12 g of t-dodecylmercaptan and 13 g of potassium peroxodisulfate. After the insideatmosphere of the polymerization vessel was replaced with nitrogen gas,1.3 kg of styrene and 3.8 kg of butadiene were charged into the vessel,and polymerization was carried out at 50° C. for 20 hours. After thepolymerization was over, the produced polymer and unreacted monomer wererecovered out of the polymerization vessel, the inside of which was thenwashed with water and residual resin was removed.

A batch of operations from the formation of the coating throughpolymerization to washing the inside of the polymerization vessel withwater as described above was repeated, the number of repeated batchesbeing given in Table 6.

After the final batch was over, in each experiment, the amount ofpolymer scale deposited on the areas in the liquid-phase region in thepolymerization vessel and the amount of polymer scale deposited on theareas around the interface between the gas and liquid phases weremeasured according to the same method as in Example 1. The results aregiven in Table 6.

Besides, to evaluate initial coloration property at the time a polymeris formed into sheet, luminosity index (L value) was measured withrespect to the polymers produced in the experiments, according to themethod below. The results are given in Table 6.

Measurement of luminosity index (L value)

To 1 kg of a polymer latex obtained was added 1 kg of 2% magnesiumsulfate solution to cause aggregation and sedimentation. The sedimentwas filtered off, washed with a hot water at 80° to 90° C. twice orthree times and dried at 40° C. for 25 hours in a vacuum dryer to give aresin.

The resin was placed in a mold measuring 9×9×0.1 cm (depth), heated at195° C. under a pressure of 50 to 60 kgf/cm² and press molded under afinal pressure of 80 kgf/cm² to prepare a test specimen. This testspecimen was measured for luminosity index L in the same manner as inExample 1.

                                      TABLE 5                                     __________________________________________________________________________    Polymer scale preventive agent                                                   (A)         (C)        Total conc.                                            Condensation                                                                         (B)  Water-soluble                                                                            of                                                  Exp.                                                                             product                                                                              Inorganic                                                                          polymeric  (A) + (B) + (C)                                                                        (A):(B):(C)                                                                         Solvent     Alkaline                 No.                                                                              No.    colloid                                                                            compound   (wt. %)  (wt. ratio)                                                                         (weight ratio)                                                                            compound                                                                            pH                 __________________________________________________________________________    201*                                                                             1      --   --         0.3      --    Water:Methanol                                                                            NaOH30)                                                                             12.5               202*                                                                             1      b    --         0.3      100:300:--                                                                          Water:Methanol                                                                            NaOH30)                                                                             12.5               203*                                                                             1      --   Na salt of carboxy-                                                                      0.3      100:--:100                                                                          Water:Methanol                                                                            NaOH30)                                                                             12.5                              methyl cellulose                                               204                                                                              1      b    Na salt of carboxy-                                                                      0.3      100:300:100                                                                         Water:Methanol                                                                            NaOH30)                                                                             12.5                              methyl cellulose                                               205                                                                              2      a    Polyacrylic acid                                                                         0.3      100:300:50                                                                          Water:Acetone (80:20)                                                                     NaOH  12.5               206                                                                              3      d    Polyvinyl pyrrolidone                                                                    0.2      100:200:50                                                                          Water:Methanol                                                                            NaOH20)                                                                             12.5               207                                                                              4      c    Casein     0.2      100:200:100                                                                         Water:Methanol                                                                            NaOH20)                                                                             12.5               __________________________________________________________________________

                  TABLE 6                                                         ______________________________________                                        Number     Results of polymerization                                          of         Polymer scale amount (g/m.sup.2)                                                                  Luminosity                                     Exp. repeated  Liquid  Around interface of                                                                         index                                    No.  batches   phase   gas and liquid phases                                                                       (L value)                                ______________________________________                                        201* 20        8       300           84.0                                     202* 30        6       250           84.0                                     203* 25        7       250           83.5                                     204  80        0       10            83.5                                     205  80        0       15            84.0                                     206  90        0       28            83.5                                     207  80        0       20            83.5                                     ______________________________________                                    

We claim:
 1. A process for producing a polymer of a monomer having anethylenically unsaturated double bond, which comprises polymerizing themonomer in a polymerization vessel having a coating on its inner wallsurfaces, whereby polymer scale is prevented from beingdeposited,wherein said coating has been formed by applying an alkalinesolution containing:(A) a condensation product of(A-1) a condensate ofacetone with a hydroxybenzene compound having at least two hydroxylgroups, and (A-2) an aldehyde compound, (B) an inorganic colloid, and(C) a water-soluble polymeric compound, followed by drying.
 2. Theprocess of claim 1, wherein said polymerization is conducted assuspension polymerization, emulsion polymerization, solutionpolymerization, bulk polymerization, or gas phase polymerization.
 3. Theprocess of claim 1, wherein said monomer comprises at least one compoundselected from the group consisting of vinyl halides; vinyl esters;acrylic acid, methacrylic acid, and their esters and salts; maleic acid,fumaric acid, and their esters and anhydrides; diene monomers; styrene;acrylonitrile; vinylidene halides; and vinyl ethers.